Mesophase deformed microstructure

Fine deformed microstructures with strong preferred orientations could be produced by a single stroke of the wire probe (25), as illustrated by Figure 17. A vertical section made on a specimen quenched immediately after deformation confirmed that the underlying structure was fibrous with tt and 2tt wedge disclinations (30). The relaxation or coarsening after deformation indicated that the mesophase was sufficiently fluid for disclination motion... 

Coke microstructure is determined by the conditions in the coalesced mesophase prior to solidification. It is determined by the combined effects of convection currents, bubble percolation, and imposed shear stresses, all of which tend to deform the mesophase. 

This paper commences with evidence for lamelliform morphologies in mesophase carbon fiber, summarizes relevant information on disclination structures in the carbonaceous mesophase, and then reviews what we learn of disclination behavior from hot-stage observations and from deformation and carbonization experiments. The results indicate that disclination interactions that occur before the mesophase is fully hardened play an important role in determining the microstructures of mesophase carbon fibers, as well as those of cokes and graphites that form through the carbonaceous mesophase. 

The carbonization experiments emphasize the need to fix or stabilize an oriented mesophase microstructure that has been imposed by mechanical deformation. The array of wedge disclinations imposed by drawing during cooldown is not thermally stable, and disclination reactions will proceed to coarsen the microstructure and reduce the preferred orientation if the mesophase softens sufficiently during carbonization. 

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